Spot-welding mechanism



Feb. 10, 1948. w. DAWSON SPOT WELDING MECHANISM Filed Feb. 1, 1943 5 Sheets-Sheet l M I EIV TOA. W

Feb. 10, 1948. J,W,,AWSON 2,435,577

SPOT WELDING MECHANISM Filed Feb. 1, 1945 3 Sheets-Sheet 2 Feb. 10, 1948. v J. w. DAWSON SPOT WELDING MECHANISM Filed Feb. 1, 1943 3 Sheets-Sheet 3.

V KM M m y M 0 W/ v J 5 atented Feta. 10, 1943 UNITED STATES r rric 15 Claims.

This invention relates to a mechanism for force to clamp 01' hold the work under proper pressure between these electrodes.

In the present practice welding machines of the spot welding type employ mechanisms which require the transmission of considerable energy to the machine. For example, in manually op erating welding machines for fabricating sheet metal parts the operator is required to move the outer end of a pedal type lever through a distance of about 19 inches. By stepping on this lever the operator cocks a large spring which in turn pulls the movable electrode into engagement with the work at a point opposite the stationary electrode. An automatic trip mechanism acti vates the Welding timer when the spring been stretched to the desired full position.

In some power operated welding mechanisms a motor-driven cam, or its equivalent, is commonly utilized to stretch or compress a spring for the purpose of applying the pressure. The motor, therefore, must be fairly large and draw a heavy line demand. In other power operated types, compressed air is used to move the electrode and apply the pressure. In such structures pistons of large diameter are required so that a safe air pressure of around sixty pounds will provide the necessary force on the electrode. Such arrangements, in which the pistons must move through a sufficient stroke to permit the electrode to span the work even though this work includes structural angles and the like, are inherently wasteful of energy.

It is among the objects of the present inventlcn to provide a mechanism which will overcome the objections outlined above and which will require the expenditure of less energy in effecting the movement of the electrode to and from the work and in the application of the required pressure upon the work, regardless of whether the mechanism is to be operated manually or by some other source of power.

To this end a mechanism is provided in which the operations are divided into two fundamentally different classes. The first operation in which the movable electrode approaches the work requires movement through some distance, but without material opposing force. This portion of the operation is therefore efiected without the expenditure of a material amount of energy except that required to overcome the riction of the system. The second operation which is effected after the electrode contacts the work involves the application of pressure without material travel. Accordingly, this operation also may be effected without the transfer or material loss of energy. Therefore, instead of building up anew the requisite "force for applying the required pressure on the electrode in this second operation, I provide a predetermined potential force, such as, the force of a previously compressed or otherwise distorted spring. The application of the force of the spring to the electrode ior each spot weld thus requires the expenditure of no :iore energy than is needed to swing the same into position.

A further objection to welding machines as at present constructed resides in the fact that the pressure brought to bear upon the work through the electrodes can be adjusted, if at all, only at great inconvenience to the operator. Furthermore, the degree of such adjustment is not satisfactory since usually adjustment through only a limited range of pressures is possible. In some machines only a few selected pressures are possible and no convenient means of selecting intermediate pressures is available. In such cases the only way in which the operator can secure the required pressure is by some undesirable expedient, such as, changing the relative position of the electrodes.

It is a further object of this invention to provide a welding mechanism which may be quickly adjusted to give any desired pressure upon the work up to a predetermined maximum value.

To this end it is a feature of the invention to provide a structure in which the force of a previously stressed spring is applied through the electrodes to the work in such a manner that its maximum component eiiective upon the work may be varied, from Zero, to the full force at which the spring has been stressed.

The above and other objects and advantages oi this invention will become apparent to those slrilled in the art from a consideration of the following detailed description taken in conjunction with the accompanying drawings in which:

Fig. 1 shows a perspective view of a welding mechanism constructed in accordance with the present invention;

Fig. 2 shows a longitudinal section through the welding mechanism and its housing structure, parts being shown in side elevation;

Fig. 3 shows a transverse section taken on line 3-4 of Fig. 2;

Fig. 4 is a diagrammatic View showing the mechanism in its normal or rest position with the electrodes open;

Fig. is a view similar to Fig. 4 but showing the parts in an intermediate position with the electrodes in contact with the work but before a material pressure has been applied thereto;

Fig. 5 is a further diagrammatic view showing the parts in full welding position with a predetermined pressure applied through the electrodes to the work; and

Fig. 7 is a view corresponding to Fig. 6, but with certain parts set in a slightly different position to which they are readily adjustable.

Referring to the drawingsjinwhich like reference numerals refer to like parts throughout the various views, reference numeral I indicates a hous lg having suitable flanges 2 for mounting the same in any desired position. A bracket 3 is mounted on one end of the housing structure to provide a support for a stationary electrode The bracket 3'iselectrically insulated from the housing l, in'accordance with usual practice and also provided with suitable screw or other fastening means forattaching a cable conn cting the electrode 4with one of the outlets a welding transformer. A lever 5 carrying a movable electrode 6 is pivoted at a point intermediate its length upon a pivot pin trode 6 contacts the work at a point opposite the stationary electrode 4 without exerting material pressure thereon. During this portion of the operation in which the lever 5 moves from the position shown in Fig. 4 to that shown in Fig. 5,

there is 'n'o'relative motion between the lever "55 and the" link to. with interior arm of the lever 5 as if fixed thereto at each" end. This is because a small com- This latter merely swings 7 ponent of the springs l3 acts in a direction to maintain the upper forked end I 2 of the link which is provided adjacent a suitable opening I S in the upper portion of the housing 5.

The free end of the lever 5 is'provided with a pivot pin 9 upon which'a link it! is hinged by means of lower forked end Ii. Link i0 is also pro.-ded with a secondforkedportion l2 at its upper end, and a pair of tension springs I3 is attached to the'up'per projecting ends of the forked portion 2. The opposite ends'of tension springs iii are attached to pivot blocks I4, which blocks are mounted upon a pair of pivot screws 55 positioned in the upwardly projecting arms E5 of a yoke it. The yoke I! is adjustably mounted upon guide rods 18 which extend longii: through the lower portion of the housadjusting screw l9, having a knob 28 projecting externally of the housing, provides e means for adjusting the yoke l'l longiof the housing I; and accordingly varying the position of the pivot screws [5 relative to the hinged joint, formed by pivot pin 9, between the lever 5 and thelink i 1.

' r 2%, which is preferably integral with, acts outwardly and downwardly from the is provided with a perforation 22 for ata steel cable" or'linkconnection to a er or other source of power. A com- .spring 23 acting between an end wall ixg i and the lower arm of the lever tends to maintain the lever 5 in its'normal posit n with the electrodes separated. A stop rod extends laterally through the housing I and is provided with aknurled screw head 25 externally of the housing for holding the stop rod any adjusted position within an arcuate slot formed in a side wall of the housing stop rod 25 thus projects into the path of movement of the link'ifi, to limit the outward swing of this link from the lever 5 to any des1- ed extent within the range of substantially 90" permitted by the slot 26. A calibrated scale 2! may be provided along the edge of the slot 25 so that the pressureconditions for any particular type of work may be repeated once a desired set 'ig has been determined.

slight pull on the cable end of iii in abutment with the lever 5 until the pivot pins has moved into-axial alignment with the pivotscrews 15 toward the end of this portion of the operation; By the end of this portion of the operation the-parts will be in the position shown in "Figi 5 with the movable electrode havingmoved into contact with the work. The lever 5 will no longer move freely in response'to' a finger 2 l,'but will be substantially immovable except for a. slight bendingupon the application of further force. The link it! will now swing'in a clockwise direction on the pivot pin 9. If'this pivot pin is in perfect alignment with the pivot screws l5 thenit will be seen that the end of the link l0 attachedto springs l3 will move through the arc of a circle having the same radius and centered upon the same axis as that through which the springs 13 swing onthe pivot screws l5. Accordingly, further pull on the'finger 2| will swing the link HJ outwardly to a position such as shownin Fig. 6, and this movement can be accomplished without varying the tension of the springs I3and without the necessity of overcoming any material force other than that required to overcome the friction of swinging the link upon its pivot'pin and of swinging the springs upon their pivot screws.

Up to the moment when the link-l0 swings outwardly the force of the springs 13, which on assembly were placed under tension, has been applied in a direction which is substantially longitudinal of the interior arm of the lever 5. Thus at first no force isapplied ina direction tending its position shown in Fig. 5 to the position shown in Fig. 6, the full force ofthesprings is applied in a direction which is substantially tangential to the arc of 'the circle described by the pivot 9. Under these conditions the'force of the springsis appliedin a direction to supply a maximum pressure upon the work. At any angle less than a lesser component of the force of the springs is described above when the parts are in the posi" effective in a-tangential direction, while the remaining component of the force may be considered as acting in a, radial direction. Accordingly, by altering thepositionof the stop rod24 any desired force within the range of the springs, that is to say within the range of the tension at which the'sprin'gs have been set,,may be applied. This ability to alter the" force applied'to'the' work without altering the initial tension setting of the springs I3 is important where the machine is to be used on different kinds of work, such as, upon sheets of different form or thickness. By means of a graduated scale 21 on the edge of the slot 26 the most favorable position of the stop rod for any particular piece of Work may be noted and the conditions duplicated for subsequent work.

A timer switch 23 may be mounted upon the stop rod 2 5 in such a position as to be contacted by the link Iii, or some contact element such as 29 connected thereto, so that the flow of welding current to the welding electrodes is initiated automatically upon the full application of the desired pressure to the work.

It will be understood that the welding circuit controlled by timer switch 28 may be of any well known type such for example as that shown in my prior U. S. Patent 2,278,430, or in numerous others, and that when so used the timer switch 28 takes the place of the usual manually operated push button controlling the welding circuit. Of course the timer switch may be omitted in which case the welding circuit may be closed by the operator after the link Hi has contacted the stop rod 24.

Although but a single embodiment of the invention has been described herein and shown in the accompanying drawings, it will be obvious to those skilled in the art that many other embodiments and variations of the device may be made in accordance with the teachings thereof and within the scope of the appended claims.

For the sake of simplicity in describing the invention, the operation has been set forth with reference to the simplest case in which the axes of rotation of the springs I3 and the links Iii coincide during the final or pressure applying operation of the device. In this particular case it will be obvious that the springs I3 will not expand or contract during this portion of the operation, except to the slight extent required by the distortion of the lever 5, or by the compression of the work between the electrodes. It will be observed, however, that this simple relation ship is not essential to the efficient operation of the device; that is to say, if the pivot pins 9 and the pivot screws I5 of the springs do not exactly coincide then there will be a slight variation in the tension of the springs during the period in which the link I is swinging outwardly from the lever. For example, if the pivot pin 9, which forms the center of rotation for the link IE6, is somewhat to the right of the position shown in Fig. 6 during this part of the operation then the tension of the springs I3 will be increased to an extent depending upon the vector distance between the centers 9 and I in the direction of the point of attachment of the springs ,I 3 at the upper forked ends of the link I0. Such slight difierence in the ultimate tension of the springs I3 makes little diii'erence in the operation of the device. The relative distance between the centers 9 and I5 during the final portion of the operation may be varied, as desired, to suit the character of the work by shifting the pivot screws i5 to the right or to the left of the position shown in Fig. 2. This adjustment of pivot screws I5 is effected by shifting the yoke II, on which they are mounted, to the right or the left by means of the knob 20 of adjusting screw I9. It will be understood that unless the pivot 9 is to the right of pivot I5 and below a line drawn between the pivot I5 and the point of attachment of springs I3 to the upper forked end of the link It, there will be noforce available to return the link In to its normal position against the interior arm of the lever 5. It is therefore preferred that the parts be positioned so that a small component of the force of the springs I3 will be effective to bias the link It in the direction of the lever 5. This position is illustrated diagrammatically in Fig. 7, from which it will be seen that a very small component of the force of springs I3 is effective to bias the link I0 toward its normal position against the lever 5, while the major component is effective to bias the lever 5 in a direction to apply pressure to the work. Obviously instead of using a small component of the force of springs I3 a separate spring could be used to bias the link It toward its normal position.

What is claimed is:

1. In a welding machine of the type having a fixed electrode and a movable electrode, means to move said movable electrode into contact with the work, means effective after such contact to apply a previously fixed force to said movable electrode, and means to limit the application of said fixed force to a predetermined component thereof to predetermine the pressure upon the work.

In a welding machine of the type having a fixed electrode and a, movable electrode, mechanism for operating said movable electrode including means to move said movable electrode into contact with the work, a restressed spring normally acting in such a direction that only a small component of its force is effective upon said movable electrode, and means, effective after said contact, to swing said spring in a direction to place an increasing component of its force upon said electrode and thereby apply pressure upon the work.

3. In a weldin machine of the type having a fixed electrode and a movable electrode, mechanism for operating said movable electrode comprising a pivoted lever, means to actuate said lever to move said movable electrode into contact with the work, a prestressed spring normally acting upon said lever in such a direction that only a small component of its force is efiective to move the same, and means, effective after said contact, to swing said spring in a direction to place an increasing component of its force upon said lever and thereby apply pressure upon the work.

4. In a welding machine of the type having a fixed electrode and a movable electrode, mechanism for operating said movable electrode comprising a pivoted lever, means to actuate said lever to move said movable electrode into contact with the work, means efiective after said contact to apply the force of a previously stressed resilient member to said movable electrode in a direction to place a predetermined pressure upon the work, and an adjustable stop member to limit the degree of pressure upon the work by limiting the angle at which the force of said resilient member is applied without materially ltering the original stress of said member.

5. In a welding machine of the type having a fixed electrode and a movable electrode, mechanism for operating said movable electrode comprising a pivoted lever, means to actuate said lever to move said movable electrode into contact with the work, a prestressed spring normally acting upon said lever in such a direction that only a small component of its force is efiective to move the same, means efiective after said contact to swing said spring in a direction to place an in;v

7 creasing component or its force upon said lever in a direction to apply pressure upon the work, and an adjustable stop member to limit the degree of pressure upon the work by limiting the angle at which said spring may act upon said lever.

6. In a Welding machine of the type having a fixed electrode and a movable electrode, mechanism for operating said movable electrode comprising a pivoted lever, means to actuate said lever to move said movable electrode into contact with the work, a resilient member normally held under a predetermined stress, and means efiective after said contact, to apply the force of said previously stressed resilient member to said movable electrode in a direction to place a predetermined pressure upon the work without materially altering the normal stress of said member.

7. In a welding machine of the type having a fixed electrode, a movable electrode and a supporting structure therefor, mechanism for operating said movable electrode comprising 'a pivoted lever, means to actuate said lever to move said movable electrode into contact with the work, a

link having one end hinged to said lever, a prestressed sprin having one end attached to said supportin structure and its other end attached to the free end of said link and only a small component of its force normally efiective to move the same, and means efiective after said contact to swing said link upon said hinge without substantially altering the stress ofsaid spring and thereby place an increasing component of the force of said spring upon said lever in a direction to apply pressure upon the work.

8. In a Welding machine of the type having a fixed electrode and a movable electrode, mechanism for operating said movable electrode comprising a pivoted lever, means to actuate said lever to move said movable electrode into contact with the work, a link having a hinged connection to said lever, a .prestressed spring normally actin through said link upon said lever in such a direction that only a small component of its force is effective in a direction tending to move 1 the same, and means effective after contact of said movable electrode with the work to swing said link upon said hinged connection and thereby apply a continuously increasing component of the force of said spring through said lever and to said electrode in a direction to place a pressure upon the work.

9. In a welding machine of the type having a fixed electrode, a movable electrode and a supporting structure therefor, mechanism for operating said movable electrode comprising an electrode lever pivoted intermediate its ends, said movable electrode being mounted at one end of said lever, a link hinged at the opposite end of said lever, said link normally extending in the general direction of the pivot point of said lever, normally stressed resilient means connected between the free end of said link and a point on the supporting structure adjacent said hinged connection between said link and said lever, means connected to said link to first swing said electrode lever into contact with the work and thereafter swing said link outwardly from said lever, to thereby apply force from said resilient means through said link to the hinged end of said electrode lever.

10. In a welding machine of the type having a fixed electrode, and a movable electrode, mechanism for operating said movable electrode comprising a pivoted lever, means to actuate said 8 lever'to move said movable electrode into contact with the work, a link having 9, hinged connection to said lever, a prestressed spring normally acting through said link upon said lever in such a direction that only a small component of its force is effective in a direction tending to move the same. means effective after said contact to swing said link upon said hinged connection and thereby apply a continuously increasing component of the force of said spring through said lever and to said electrode in a direction to place a pressure upon the work, a stop member, and means to adjustably position said stop member in the path of movement of said link to limit the angle through which said link may swing uponsaid hinged connection and accordingly limit the angle at which the stress of said spring is applied to said lever.

11. In a welding machine of the type having a fixed electrode, and a movable electrode,.mecha- .nism for operating said movable electrode comprising a pivoted lever, means to actuate said lever to move said movable electrode into contact with the work, a link having a hinged connection to said lever, a prestressed spring normally acting through said link upon said lever in such a direction that only a small component of its force is effective in a direction tending to move the same, means effective after said contact to swing said link upon said hinged connection and thereby apply a continuously increasing component of the force of said spring through said lever and to said electrode in a direction to place a pressure upon the work, means to limit the angle through which said link may swing upon said hinged connection and accordingly limit the angle at which the stress of said spring is applied to said lever, and a switch operable by said link at the limit of its swing to control the welding circuit supplying current to said electrodes.

12. In a welding machine of the type having a supporting structure, a fixed electrode, and a movable electrode, mechanism for operating said movable electrode comprising an electrode lever pivoted intermediate its ends, said movable electrode being mounted at one end of said lever, a link hinged at the opposite end of said lever, said link normally extending in the general direction of the pivot point of said electrode lever, normally stressed resilient means connected between the free end of said link and a point on the supporting structure adjacent said hinged connection between said link and said lever, means connected to said link to first swing said electrode lever into contact with the work and thereafter swing said link outwardly from said lever to thereby apply force from said resilient means through said link to the hinged end of said electrode lever, a stop member, and means to adjustably position said stop member in the path of movement of said link to limit the angle through which said link may swing upon said hinged connection and accordingly limit the angle at which the stress of said spring is applied to said lever.

13. In a, welding machine of the type having a supporting structure, a fixed electrode, and a movable electrode, mechanism for operating said movable electrode comprising an electrode lever pivoted intermediate its ends, said movable electrode being mounted at one end of said lever, a link hinged at the opposite end of said lever, said link normally extending in the general direction of the pivot point of said electrode lever, normally stressed resilient means connected between the free end of said link and a point on the supporting structure adjacent said hinged connection between said link and said lever, means connected to said link to first swing said electrode lever into contact with the work and thereafter swing said link outwardly from said lever to thereby apply force from said resilient means through said link to the hinged end of said electrode lever, a stop member, means to adjustably position said stop member in the path of movement of said link to limit the angle through which said link may swing upon said hinged connection and accordingly limit the angle at whicnthe stress of said spring is applied to said lever, and

such contact to exert a previously generated force through said electrodes thereby placing a pressure upon the work, means to relieve said pressure without material expenditure of said force, and means for adjusting the magnitude of said pressure by altering the direction in which said force is applied.

JOHN W. DAWSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,579,721 Leslie Apr. 6, 1926 1,728,616 Kondakjian Sept. 17, 1929 1,869,188 Eckman July 26, 1932 1,996,679 Lepek Apr. 2, 1935 2,251,957 Rainville Aug. 12, 1941 1,698,656 Ream Jan. 8, 1929 1,813,801 Haynes July 7, 1931 FOREIGN PATENTS Number Country Date 4 430,768 Great Britain June 25, 1935 

